The present invention generally relates to fuel-fired heating appliances and, in a preferred embodiment thereof, more particularly provides a gas-fired water heater having incorporated therein a specially designed flammable vapor sensor-based burner shut-off system.
Gas-fired residential and commercial water heaters are generally formed to include a vertical cylindrical water storage tank with a gas burner disposed in a combustion chamber below the tank. The burner is supplied with fuel gas through a valved gas supply line, and combustion air through an air inlet flow path providing communication between the exterior of the water heater and the interior of the combustion chamber.
Water heaters of this general type are extremely safe and quite reliable in operation. However, when gasoline or other flammable liquids are stored or used improperly in proximity to the water heater, there may exist a possibility of flammable vapors becoming entrained in the air intake of the water heater. It is theorized that such vapors might cause secondary combustion to occur within the confines of the water heater combustion chamber.
In view of this, various modern gas-fired water heater designs, as well as the designs of other types of fuel-fired heating appliances, focus upon the preclusion of fuel flow to the appliance when extraneous flammable vapors are present exteriorly adjacent the appliance. It is to this design goal that the present invention is directed.
In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a fuel-fired heating apparatus is provided with a specially designed system for shutting off fuel flow to the apparatus when flammable vapors are exteriorly adjacent thereto. Representatively, the fuel-fired heating apparatus is a gas-fired water heater. However, principles of this invention are also applicable to other types of fuel-fired heating apparatus such as, for example, boilers and air heating furnaces.
The water heater representatively comprises a tank for holding water to be heated, the tank being disposed within a jacket structure defining a vertically extending insulation cavity circumscribing the tank, and a combustion chamber disposed beneath the tank in thermal communication therewith. A burner structure is disposed within the combustion chamber and is operative to create hot combustion products therein, and a fuel valve is coupled to the burner structure and is operative to supply fuel thereto. A flue communicates with the combustion chamber and extends upwardly through the tank, and a draft structure is coupled to the flue and is operative to create a draft that draws the created hot combustion products upwardly through the flue. In a power vented embodiment of the water heater, the draft structure includes a draft inducer fan, and in a natural draft embodiment of the water heater the draft structure may include an upward extension of the flue.
The fuel supply shut-off system associated with the water heater illustratively comprises a flammable vapor senor and a conduit structure in the form of an induced flow tube. The sensor is positioned and operative to be engaged by and detect flammable vapors exteriorly adjacent the water heater and responsively preclude delivery of fuel from the valve to the burner structure. The conduit structure is communicated with the draft structure, extends to adjacent the sensor, and defines a flow path isolated from the combustion chamber.
The conduit structure is operative to utilize the natural or forced draft of the water heater to forcibly draw adjacent flammable vapors across the sensor and then to the draft structure through the flow path within the conduit structure. Because of this biased flow of flammable vapors through the conduit structure and across the sensor, the contact of the vapors with the sensor is substantially facilitated as compared to simply permitting the vapors to migrate into operative contact with the sensor.
In various illustrative embodiments of the water heater, the conduit or flow tube structure (1) is an integral portion of the water heater jacket structure, (2) is a separate structure which extends externally along the jacket structure, (3) extends upwardly through the combustion chamber and the flue, (4) extends through the tank, or (5) extends through the insulation cavity. Preferably, the water heater further comprises an arrestor plate structure defining a bottom exterior wall portion of the combustion chamber and having a spaced series of flame quenching combustion air inlet openings therein.